Active matrix and other types of LCDs are increasingly being used as display devices in aircraft. To accommodate low level night operation and high ambient sunlight conditions, an extremely large backlight dimming range is necessary. A desired luminance range may be as large 0.03 FtL to 200 FtL (6667:1) over the display field of view. This is a much larger range than previously exhibited by typical hot cathode or cold cathode fluorescent lamps.
Previous backlight designs for backlighting LCDs have exhibited a limited luminance range of only approximately 2000:1 for hot cathode lamps and 500:1 for cold cathode lamps. Conventional backlight designs cannot typically achieve the low end of the luminance range without the fluorescent lamp extinguishing or flickering. Since the difficulty in providing the extremely large dimming range occurs primarily at very low luminance levels, a backlight design capable of operating the fluorescent lamp to achieve a very low luminance uniform output would be a significant improvement. Also, previous backlight designs require both high voltage and high current to start at temperatures below 0.degree. C. Frequently, the high voltage and current cause damage and premature failure of the anode and cathode of the lamp. A backlight capable of low temperature start-ups, with lower voltages and currents which will not damage the anode and cathode, would likewise be an improvement in the art.